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Kalvapalle PB, Sridhar S, Silberg JJ, Stadler LB. Long-duration environmental biosensing by recording analyte detection in DNA using recombinase memory. Appl Environ Microbiol 2024; 90:e0236323. [PMID: 38551351 PMCID: PMC11022584 DOI: 10.1128/aem.02363-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Accepted: 02/20/2024] [Indexed: 04/18/2024] Open
Abstract
Microbial biosensors that convert environmental information into real-time visual outputs are limited in their sensing abilities in complex environments, such as soil and wastewater, due to optical inaccessibility. Biosensors that could record transient exposure to analytes within a large time window for later retrieval represent a promising approach to solve the accessibility problem. Here, we test the performance of recombinase-memory biosensors that sense a sugar (arabinose) and a microbial communication molecule (3-oxo-C12-L-homoserine lactone) over 8 days (~70 generations) following analyte exposure. These biosensors sense the analyte and trigger the expression of a recombinase enzyme which flips a segment of DNA, creating a genetic memory, and initiates fluorescent protein expression. The initial designs failed over time due to unintended DNA flipping in the absence of the analyte and loss of the flipped state after exposure to the analyte. Biosensor performance was improved by decreasing recombinase expression, removing the fluorescent protein output, and using quantitative PCR to read out stored information. Application of memory biosensors in wastewater isolates achieved memory of analyte exposure in an uncharacterized Pseudomonas isolate. By returning these engineered isolates to their native environments, recombinase-memory systems are expected to enable longer duration and in situ investigation of microbial signaling, cross-feeding, community shifts, and gene transfer beyond the reach of traditional environmental biosensors.IMPORTANCEMicrobes mediate ecological processes over timescales that can far exceed the half-lives of transient metabolites and signals that drive their collective behaviors. We investigated strategies for engineering microbes to stably record their transient exposure to a chemical over many generations through DNA rearrangements. We identify genetic architectures that improve memory biosensor performance and characterize these in wastewater isolates. Memory biosensors are expected to be useful for monitoring cell-cell signals in biofilms, detecting transient exposure to chemical pollutants, and observing microbial cross-feeding through short-lived metabolites within cryptic methane, nitrogen, and sulfur cycling processes. They will also enable in situ studies of microbial responses to ephemeral environmental changes, or other ecological processes that are currently challenging to monitor non-destructively using real-time biosensors and analytical instruments.
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Affiliation(s)
| | - Swetha Sridhar
- Systems, Synthetic, and Physical Biology Graduate Program, Rice University, Houston, Texas, USA
| | - Jonathan J. Silberg
- Department of BioSciences, Rice University, Houston, Texas, USA
- Department of Bioengineering, Rice University, Houston, Texas, USA
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, USA
| | - Lauren B. Stadler
- Department of Civil and Environmental Engineering, Rice University, Houston, Texas, USA
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2
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Tsukimi T, Obana N, Shigemori S, Arakawa K, Miyauchi E, Yang J, Song I, Ashino Y, Wakayama M, Soga T, Tomita M, Ohno H, Mori H, Fukuda S. Genetic mutation in Escherichia coli genome during adaptation to the murine intestine is optimized for the host diet. mSystems 2024; 9:e0112323. [PMID: 38205998 PMCID: PMC10878103 DOI: 10.1128/msystems.01123-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 11/15/2023] [Indexed: 01/12/2024] Open
Abstract
Mammalian gut microbes colonize the intestinal tract of their host and adapt to establish a microbial ecosystem. The host diet changes the nutrient profile of the intestine and has a high impact on microbiota composition. Genetic mutations in Escherichia coli, a prevalent species in the human gut, allow for adaptation to the mammalian intestine, as reported in previous studies. However, the extent of colonization fitness in the intestine elevated by genetic mutation and the effects of diet change on these mutations in E. coli are still poorly known. Here, we show that notable mutations in sugar metabolism-related genes (gatC, araC, and malI) were detected in the E. coli K-12 genome just 2 weeks after colonization in the germ-free mouse intestine. In addition to elevated fitness by deletion of gatC, as previously reported, deletion of araC and malI also elevated E. coli fitness in the murine intestine in a host diet-dependent manner. In vitro cultures of medium containing nutrients abundant in the intestine (e.g., galactose, N-acetylglucosamine, and asparagine) also showed increased E. coli fitness after deletion of the genes-of-interest associated with their metabolism. Furthermore, the host diet was found to influence the developmental trajectory of gene mutations in E. coli. Taken together, we suggest that genetic mutations in E. coli are selected in response to the intestinal environment, which facilitates efficient utilization of nutrients abundant in the intestine under laboratory conditions. Our study offers some insight into the possible adaptation mechanisms of gut microbes.IMPORTANCEThe gut microbiota is closely associated with human health and is greatly impacted by the host diet. Bacteria such as Escherichia coli live in the gut all throughout the life of a human host and adapt to the intestinal environment. Adaptive mutations in E. coli are reported to enhance fitness in the mammalian intestine, but to what extent is still poorly known. It is also unknown whether the host diet affects what genes are mutated and to what extent fitness is affected. This study suggests that genetic mutations in the E. coli K-12 strain are selected in response to the intestinal environment and facilitate efficient utilization of abundant nutrients in the germ-free mouse intestine. Our study provides a better understanding of these intestinal adaptation mechanisms of gut microbes.
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Affiliation(s)
- Tomoya Tsukimi
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
| | - Nozomu Obana
- Transborder Medical Research Center, Institute of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Suguru Shigemori
- Transborder Medical Research Center, Institute of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Kazuharu Arakawa
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
- Faculty of Environment and Information Studies, Keio University, Fujisawa, Japan
| | - Eiji Miyauchi
- RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Jiayue Yang
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
| | - Isaiah Song
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
| | - Yujin Ashino
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
| | - Masataka Wakayama
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
| | - Tomoyoshi Soga
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
- Faculty of Environment and Information Studies, Keio University, Fujisawa, Japan
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
- Faculty of Environment and Information Studies, Keio University, Fujisawa, Japan
| | - Hiroshi Ohno
- RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Hirotada Mori
- Graduate School of Biological Science, Nara Institute of Science and Technology, Ikoma, Japan
- Institute of Animal Sciences, Guangdong Academy of Agricultural Sciences, Guangzhou, Guangdong, China
| | - Shinji Fukuda
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Japan
- Transborder Medical Research Center, Institute of Medicine, University of Tsukuba, Tsukuba, Japan
- Gut Environmental Design Group, Kanagawa Institute of Industrial Science and Technology, Kawasaki, Japan
- Laboratory for Regenerative Microbiology, Juntendo University Graduate School of Medicine, Tokyo, Japan
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3
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Chen X, Kaiser CM. AP profiling resolves co-translational folding pathway and chaperone interactions in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555749. [PMID: 37693575 PMCID: PMC10491307 DOI: 10.1101/2023.09.01.555749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Natural proteins have evolved to fold robustly along specific pathways. Folding begins during synthesis, guided by interactions of the nascent protein with the ribosome and molecular chaperones. However, the timing and progression of co-translational folding remain largely elusive, in part because the process is difficult to measure in the natural environment of the cytosol. We developed a high-throughput method to quantify co-translational folding in live cells that we term Arrest Peptide profiling (AP profiling). We employed AP profiling to delineate co-translational folding for a set of GTPase domains with very similar structures, defining how topology shapes folding pathways. Genetic ablation of major nascent chain-binding chaperones resulted in localized folding changes that suggest how functional redundancies among chaperones are achieved by distinct interactions with the nascent protein. Collectively, our studies provide a window into cellular folding pathways of complex proteins and pave the way for systematic studies on nascent protein folding at unprecedented resolution and throughput.
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Affiliation(s)
- Xiuqi Chen
- CMDB Graduate Program, Johns Hopkins University, Baltimore, MD, United States
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States
- Present address: Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Christian M. Kaiser
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, United States
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4
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Wichmann J, Behrendt G, Boecker S, Klamt S. Characterizing and utilizing oxygen-dependent promoters for efficient dynamic metabolic engineering. Metab Eng 2023; 77:199-207. [PMID: 37054967 DOI: 10.1016/j.ymben.2023.04.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 04/03/2023] [Accepted: 04/10/2023] [Indexed: 04/15/2023]
Abstract
Promoters adjust cellular gene expression in response to internal or external signals and are key elements for implementing dynamic metabolic engineering concepts in fermentation processes. One useful signal is the dissolved oxygen content of the culture medium, since production phases often proceed in anaerobic conditions. Although several oxygen-dependent promoters have been described, a comprehensive and comparative study is missing. The goal of this work is to systematically test and characterize 15 promoter candidates that have been previously reported to be induced upon oxygen depletion in Escherichia coli. For this purpose, we developed a microtiter plate-level screening using an algal oxygen-independent flavin-based fluorescent protein and additionally employed flow cytometry analysis for verification. Various expression levels and dynamic ranges could be observed, and six promoters (nar-strong, nar-medium, nar-weak, nirB-m, yfiD-m, and fnrF8) appear particularly suited for dynamic metabolic engineering applications. We demonstrate applicability of these candidates for dynamic induction of enforced ATP wasting, a metabolic engineering approach to increase productivity of microbial strains that requires a narrow level of ATPase expression for optimal function. The selected candidates exhibited sufficient tightness under aerobic conditions while, under complete anaerobiosis, driving expression of the cytosolic F1-subunit of the ATPase from E. coli to levels that resulted in unprecedented specific glucose uptake rates. We finally utilized the nirB-m promoter to demonstrate the optimization of a two-stage lactate production process by dynamically enforcing ATP wasting, which is automatically turned on in the anaerobic (growth-arrested) production phase to boost the volumetric productivity. Our results are valuable for implementing metabolic control and bioprocess design concepts that use oxygen as signal for regulation and induction.
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Affiliation(s)
- Julian Wichmann
- Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106, Magdeburg, Germany
| | - Gerrich Behrendt
- Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106, Magdeburg, Germany
| | - Simon Boecker
- Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106, Magdeburg, Germany
| | - Steffen Klamt
- Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106, Magdeburg, Germany.
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5
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Sugiyama R, Suarez AFL, Morishita Y, Nguyen TQN, Tooh YW, Roslan MNHB, Lo Choy J, Su Q, Goh WY, Gunawan GA, Wong FT, Morinaka BI. The Biosynthetic Landscape of Triceptides Reveals Radical SAM Enzymes That Catalyze Cyclophane Formation on Tyr- and His-Containing Motifs. J Am Chem Soc 2022; 144:11580-11593. [PMID: 35729768 DOI: 10.1021/jacs.2c00521] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Peptide-derived cyclophanes inhabit a unique niche in the chemical space of macrocyclic peptides with several examples of pharmaceutical importance. Although both synthetic and biocatalytic methods are available for constructing these macrocycles, versatile (bio)catalysts able to incorporate a variety of amino acids that compose the macrocycle would be useful for the creation of diverse peptide cyclophanes. In this report, we synergized the use of bioinformatic tools to map the biosynthetic landscape of radical SAM enzymes (3-CyFEs) that catalyze three-residue cyclophane formation in the biosynthesis of a new family of RiPP natural products, the triceptides. This analysis revealed 3940 (3113 unique) putative precursor sequences predicted to be modified by 3-CyFEs. Several uncharacterized maturase systems were identified that encode unique precursor types. Functional studies were carried out in vivo in Escherichia coli to identify modified precursors containing His and Tyr residues. NMR analysis of the products revealed that Tyr and His can also be incorporated into cyclophane macrocycles by 3-CyFEs. Collectively, all aromatic amino acids can be incorporated by 3-CyFEs, and the cyclophane formation strictly occurs via a C(sp2)-C(sp3) cross-link between the (hetero)aromatic ring to Cβ. In addition to 3-CyFEs, we functionally validated an Fe(II)/α-ketoglutarate-dependent hydroxylase, resulting in β-hydroxylated residues within the cyclophane rings. This study reveals the potential breadth of triceptide precursors and a systematic approach for studying these enzymes to broaden the diversity of peptide macrocycles.
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Affiliation(s)
- Ryosuke Sugiyama
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | | | - Yohei Morishita
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | - Thi Quynh Ngoc Nguyen
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | - Yi Wei Tooh
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | | | - Justin Lo Choy
- Department of Pharmacology and Toxicology, University of Toronto, Toronto M5S 1A8, Canada
| | - Qi Su
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | - Wei Yang Goh
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
| | - Gregory Adrian Gunawan
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore.,Molecular Engineering Lab, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore.,Organic & Biomolecular Chemistry, Institute of Sustainability for Chemicals, Energy and Environment, A*STAR, Singapore 138665, Singapore
| | - Fong Tian Wong
- Molecular Engineering Lab, Institute of Molecular and Cell Biology, A*STAR, Singapore 138673, Singapore.,Singapore Institute of Food and Biotechnology Innovation, A*STAR, Singapore 138673, Singapore
| | - Brandon I Morinaka
- Department of Pharmacy, National University of Singapore, Singapore 117544, Singapore
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6
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Meng W, Qiao K, Zhang W, Liu F, Gao X, Hu X, Zhu J. Development and Application of a New Arabinose-Inducible Vector in High-Attachment Strain Stenotrophomonas AGS-1 from Aerobic Granular Sludge. ACS Synth Biol 2022; 11:69-76. [PMID: 34989221 DOI: 10.1021/acssynbio.1c00446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To explore the molecular structure of attachment genes, we constructed and characterized a new arabinose-inducible vector for the high-attachment strain Stenotrophomonas AGS-1 isolated from aerobic granular sludge (AGS). mCherry was used as a simple observation biomarker, and the araC-PBAD-inducible promoter was chosen to artificially regulate the expression of target genes. The system achieved little leaky basal expression and high maximal induced expression. The araC-PBAD-based inducible expression was modulated over a wide range of 0.0005 to 0.2% l-arabinose. Notably, a "lag expression" phenomenon was observed in which mCherry was expressed after bacterial growth in LB medium. Using the system and the strategy of fusion expression of target genes (rmlA and AsCas12a) plus mCherry, the recombinant AGS-1 strain achieved the effective induction of rmlA and AsCas12a-mCherry gene expression in the range of 0.0005 to 0.1% l-arabinose. These results demonstrate that the new arabinose-inducible vector could be used as an important molecular tool in the gene function and genome-editing research of strain AGS-1.
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Affiliation(s)
- Wei Meng
- School of Environment, Beijing Normal University, Beijing 100875, China
- R & D Centre of Aerobic Granule Technology, Beijing 100875, China
| | - Kai Qiao
- School of Environment, Beijing Normal University, Beijing 100875, China
- State Key Laboratory of Water Simulation, Beijing 100875, China
| | - Wei Zhang
- School of Environment, Beijing Normal University, Beijing 100875, China
- R & D Centre of Aerobic Granule Technology, Beijing 100875, China
| | - Fan Liu
- School of Environment, Beijing Normal University, Beijing 100875, China
| | - Xu Gao
- School of Environment, Beijing Normal University, Beijing 100875, China
| | - Xuan Hu
- School of Environment, Beijing Normal University, Beijing 100875, China
- State Key Laboratory of Water Simulation, Beijing 100875, China
| | - Jianrong Zhu
- School of Environment, Beijing Normal University, Beijing 100875, China
- R & D Centre of Aerobic Granule Technology, Beijing 100875, China
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7
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Cautionary Notes on the Use of Arabinose- and Rhamnose-Inducible Expression Vectors in Pseudomonas aeruginosa. J Bacteriol 2021; 203:e0022421. [PMID: 34096777 DOI: 10.1128/jb.00224-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Pseudomonas aeruginosa virulence factor regulator (Vfr) is a cyclic AMP (cAMP)-responsive transcription factor homologous to the Escherichia coli cAMP receptor protein (CRP). Unlike CRP, which plays a central role in E. coli energy metabolism and catabolite repression, Vfr is primarily involved in the control of P. aeruginosa virulence factor expression. Expression of the Vfr regulon is controlled at the level of vfr transcription, Vfr translation, cAMP synthesis, and cAMP degradation. While investigating mechanisms that regulate Vfr translation, we placed vfr transcription under the control of the rhaBp rhamnose-inducible promoter system (designated PRha) and found that PRha promoter activity was highly dependent upon vfr. Vfr dependence was also observed for the araBp arabinose-inducible promoter (designated PBAD). The observation of Vfr dependence was not entirely unexpected. Both promoters are derived from E. coli, where maximal promoter activity is dependent upon CRP. Like CRP, we found that Vfr directly binds to promoter probes derived from the PRha and PBAD promoters in vitro. Because Vfr-cAMP activity is highly integrated into numerous global regulatory systems, including c-di-GMP signaling, the Gac/Rsm system, MucA/AlgU/AlgZR signaling, and Hfq/sRNAs, the potential exists for significant variability in PRha and PBAD promoter activity in a variety of genetic backgrounds, and use of these promoter systems in P. aeruginosa should be employed with caution. IMPORTANCE Heterologous gene expression and complementation constitute a valuable and widely utilized tool in bacterial genetics. The arabinose-inducible ParaBAD (PBAD) and rhamnose-inducible PrhaBAD (PRha) promoter systems are commonly used in P. aeruginosa genetics and prized for the tight control and dynamic expression ranges that can be achieved. In this study, we demonstrate that the activity of both promoters is dependent upon the cAMP-dependent transcription factor Vfr. While this poses an obvious problem for use in a vfr mutant background, the issue is more pervasive, considering that vfr transcription/synthesis and cAMP homeostasis are highly integrated into the cellular physiology of the organism and influenced by numerous global regulatory systems. Fortunately, the synthetic PTac promoter is not subject to Vfr regulatory control.
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8
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Crozier L, Marshall J, Holmes A, Wright KM, Rossez Y, Merget B, Humphris S, Toth I, Jackson RW, Holden NJ. The role of l-arabinose metabolism for Escherichia coli O157:H7 in edible plants. MICROBIOLOGY (READING, ENGLAND) 2021; 167:001070. [PMID: 34319868 PMCID: PMC8489885 DOI: 10.1099/mic.0.001070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/11/2021] [Indexed: 12/12/2022]
Abstract
Arabinose is a major plant aldopentose in the form of arabinans complexed in cell wall polysaccharides or glycoproteins (AGP), but comparatively rare as a monosaccharide. l-arabinose is an important bacterial metabolite, accessed by pectolytic micro-organisms such as Pectobacterium atrosepticum via pectin and hemicellulose degrading enzymes. However, not all plant-associated microbes encode cell-wall-degrading enzymes, yet can metabolize l-arabinose, raising questions about their use of and access to the glycan in plants. Therefore, we examined l-arabinose metabolism in the food-borne pathogen Escherichia coli O157:H7 (isolate Sakai) during its colonization of plants. l-arabinose metabolism (araBA) and transport (araF) genes were activated at 18 °C in vitro by l-arabinose and expressed over prolonged periods in planta. Although deletion of araBAD did not impact the colonization ability of E. coli O157:H7 (Sakai) on spinach and lettuce plants (both associated with STEC outbreaks), araA was induced on exposure to spinach cell-wall polysaccharides. Furthermore, debranched and arabinan oligosaccharides induced ara metabolism gene expression in vitro, and stimulated modest proliferation, while immobilized pectin did not. Thus, E. coli O157:H7 (Sakai) can utilize pectin/AGP-derived l-arabinose as a metabolite. Furthermore, it differs fundamentally in ara gene organization, transport and regulation from the related pectinolytic species P. atrosepticum, reflective of distinct plant-associated lifestyles.
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Affiliation(s)
- Louise Crozier
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
| | | | - Ashleigh Holmes
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
| | | | - Yannick Rossez
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
- Université de Technologie de Compiègne, CNRS-FRE 3580, Centre de Recherche de Royallieu, 60203 COMPIEGNE CEDEX, France
| | - Bernhard Merget
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
| | - Sonia Humphris
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
| | - Ian Toth
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
| | - Robert Wilson Jackson
- School of Biological Sciences, The University of Reading, Reading, UK
- Birmingham Institute of Forest Research and School of Biosciences University of Birmingham, Birmingham B15 2TT, UK
| | - Nicola Jean Holden
- The James Hutton Institute, Cell & Molecular Sciences, Dundee, DD2 5DA, UK
- SRUC, Department of Rural Land Use, Aberdeen, AB21 9YA, UK
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9
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Asplund-Samuelsson J, Hudson EP. Wide range of metabolic adaptations to the acquisition of the Calvin cycle revealed by comparison of microbial genomes. PLoS Comput Biol 2021; 17:e1008742. [PMID: 33556078 PMCID: PMC7895386 DOI: 10.1371/journal.pcbi.1008742] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 02/19/2021] [Accepted: 01/25/2021] [Indexed: 11/21/2022] Open
Abstract
Knowledge of the genetic basis for autotrophic metabolism is valuable since it relates to both the emergence of life and to the metabolic engineering challenge of incorporating CO2 as a potential substrate for biorefining. The most common CO2 fixation pathway is the Calvin cycle, which utilizes Rubisco and phosphoribulokinase enzymes. We searched thousands of microbial genomes and found that 6.0% contained the Calvin cycle. We then contrasted the genomes of Calvin cycle-positive, non-cyanobacterial microbes and their closest relatives by enrichment analysis, ancestral character estimation, and random forest machine learning, to explore genetic adaptations associated with acquisition of the Calvin cycle. The Calvin cycle overlaps with the pentose phosphate pathway and glycolysis, and we could confirm positive associations with fructose-1,6-bisphosphatase, aldolase, and transketolase, constituting a conserved operon, as well as ribulose-phosphate 3-epimerase, ribose-5-phosphate isomerase, and phosphoglycerate kinase. Additionally, carbohydrate storage enzymes, carboxysome proteins (that raise CO2 concentration around Rubisco), and Rubisco activases CbbQ and CbbX accompanied the Calvin cycle. Photorespiration did not appear to be adapted specifically for the Calvin cycle in the non-cyanobacterial microbes under study. Our results suggest that chemoautotrophy in Calvin cycle-positive organisms was commonly enabled by hydrogenase, and less commonly ammonia monooxygenase (nitrification). The enrichment of specific DNA-binding domains indicated Calvin-cycle associated genetic regulation. Metabolic regulatory adaptations were illustrated by negative correlation to AraC and the enzyme arabinose-5-phosphate isomerase, which suggests a downregulation of the metabolite arabinose-5-phosphate, which may interfere with the Calvin cycle through enzyme inhibition and substrate competition. Certain domains of unknown function that were found to be important in the analysis may indicate yet unknown regulatory mechanisms in Calvin cycle-utilizing microbes. Our gene ranking provides targets for experiments seeking to improve CO2 fixation, or engineer novel CO2-fixing organisms.
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Affiliation(s)
- Johannes Asplund-Samuelsson
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Solna, Sweden
| | - Elton P. Hudson
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Solna, Sweden
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10
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Riedl A, Gruber S, Ruzsics Z. Novel conditional plasmids regulated by chemical switches provide versatile tools for genetic engineering in Escherichia coli. Plasmid 2020; 111:102531. [PMID: 32920019 DOI: 10.1016/j.plasmid.2020.102531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 07/07/2020] [Accepted: 08/08/2020] [Indexed: 02/01/2023]
Abstract
Engineering bacterial genomes or foreign DNA cloned as bacterial artificial chromosomes (BACs) relies on usage of helper plasmids, which deliver the desired tools transiently into the bacteria to be modified. After the anticipated action is completed the helper plasmids need to be cured. To make this efficient, plasmids are used that are maintained by conditional amplicons or carry a counter-selection marker. Here, we describe new conditional plasmids that can be maintained or cured by using chemical induction or repression. Our method is based on the dependency of plasmids carrying ori6Kγ origin of replication on the presence of protein Π. Ori6Kγ based plasmids are tightly regulated conditional constructs, but they require usually special E. coli strains to operate. To avoid this, we placed the Π protein expression under the control of a co-expressed conditional repressor. Regulating the maintenance of plasmids with administration or removal of chemicals is fully compatible with any other conditional amplicons applied to date. Here, we describe methods for inducing sites specific recombination of BACs as an example. However, the same strategy might be used to construct appropriate helper plasmids for any other transient components of genome editing methodologies such as λred recombinases or CRISPR/Cas components.
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Affiliation(s)
- André Riedl
- Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| | - Simone Gruber
- Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| | - Zsolt Ruzsics
- Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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11
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Román R, Lončar N, Casablancas A, Fraaije MW, Gonzalez G. High-level production of industrially relevant oxidases by a two-stage fed-batch approach: overcoming catabolite repression in arabinose-inducible Escherichia coli systems. Appl Microbiol Biotechnol 2020; 104:5337-5345. [PMID: 32322946 DOI: 10.1007/s00253-020-10622-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/03/2020] [Accepted: 04/13/2020] [Indexed: 12/21/2022]
Abstract
With the growing interest in enzyme applications, there is an urgent demand for economic, affordable, and flexible enzyme production processes. In the present paper, we developed a high cell density fed-batch process for the production of two cofactor-containing oxidase, 5-hydroxymethylfurfural oxidase (HMFO) and eugenol oxidase (EUGO). The approach involved the arabinose-inducible system to drive the expression while using mineral media. In order to overcome a major drawback of arabinose-inducible promoters, carbon catabolite repression, (CCR) by glucose, we developed a high cell density culture (HCDC), two-stage fed-batch protocol allowing us to reach cell densities exceeding 70 g/L of dry cell weight (DCW) using glucose as carbon source. Then, induction was achieved by adding arabinose, while changing the carbon source to glycerol. This strategy allowed us to obtain an eightfold increase in recombinant HMFO titer when compared with a reference batch fermentation in Erlenmeyer flasks using terrific broth (TB), typically used with arabinose-inducible strains. The optimized protocol was also tested for expression of a structurally unrelated oxidase, EUGO, where a similar yield was achieved. Clearly, this two-step protocol in which a relatively cheap medium (when compared to TB) can be used reduces costs and provides a way to obtain protein production levels similar to those of IPTG-based systems. KEY POINTS: • Arabinose promoters are not well suited for HCDC production due to CCR effect. • This drawback has been overcome by using a two-stage Fed-batch protocol. • Protein yield has been increased by an eightfold factor, improving process economics.
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Affiliation(s)
- Ramón Román
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain.
| | | | - Antoni Casablancas
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
| | - Marco W Fraaije
- Molecular Enzymology group, University of Groningen, Groningen, The Netherlands
| | - Glòria Gonzalez
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
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12
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Abstract
Escherichia coli BL21-AI is a commercially available strain possessing a phage T7-based protein-expression system. A combination of tight regulation and high yield makes it widely used for high-level expression of toxic recombinant proteins. Here, we present the complete genome sequence of BL21-AI and provide insights on its genome.
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13
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Alva A, Sabido-Ramos A, Escalante A, Bolívar F. New insights into transport capability of sugars and its impact on growth from novel mutants of Escherichia coli. Appl Microbiol Biotechnol 2020; 104:1463-1479. [PMID: 31900563 DOI: 10.1007/s00253-019-10335-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/12/2019] [Accepted: 12/27/2019] [Indexed: 12/27/2022]
Abstract
The fast-growing capability of Escherichia coli strains used to produce industrially relevant metabolites relies on their capability to transport efficiently glucose or potential industrial feedstocks such as sucrose or xylose as carbon sources. E. coli imports extracellular glucose into the periplasmic space across the outer membrane porins: OmpC, OmpF, and LamB. As the internal membrane is an impermeable barrier for sugars, the cell employs several primary and secondary active transport systems, and the phosphoenolpyruvate (PEP)-sugar phosphotransferase (PTS) system for glucose transport. PTS:glucose is the preferred system by E. coli to transport and phosphorylate the periplasmic glucose; nevertheless, PTS imposes a strict metabolic control mechanism on the preferential consumption of glucose over other carbon sources in sugar mixtures such as glucose and xylose resulting from the hydrolysis of lignocellulosic biomass, by the carbon catabolite repression. In this contribution, we summarize the major sugar transport systems for glucose and disaccharide transport, the exhibited substrate plasticity, and their impact on the growth of E. coli, highlighting the relevance of PTS in the control of the expression of genes for the transport and catabolism of other sugars as xylose. We discuss the strategies developed by evolved mutants of E. coli during adaptive laboratory evolution experiments to overcome the nutritional stress condition imposed by inactivation of PTS as a strategy for the selection of fast-growing derivatives in glucose, xylose, or mixtures of glucose:xylose. This approach results in the recruitment of other primary and secondary active transporters, demonstrating relevant sugar plasticity in derivative-evolved mutants. Elucidation of the molecular and biochemical basis of sugar-transport substrate plasticity represents a consistent approach for sugar-transport system engineering for the design of efficient E. coli derivative strains with improved substrate assimilation for biotechnological purposes.
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Affiliation(s)
- Alma Alva
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Andrea Sabido-Ramos
- Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana-Unidad Cuajimalpa, Ciudad de México, México
| | - Adelfo Escalante
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
| | - Francisco Bolívar
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
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14
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Pu M, Storms E, Chodur DM, Rowe-Magnus DA. Calcium-dependent site-switching regulates expression of the atypical iam pilus locus in Vibrio vulnificus. Environ Microbiol 2019; 22:4167-4182. [PMID: 31355512 DOI: 10.1111/1462-2920.14763] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Accepted: 07/25/2019] [Indexed: 12/21/2022]
Abstract
The opportunistic human pathogen Vibrio vulnificus inhabits warm coastal waters and asymptomatically colonizes seafood, most commonly oysters. We previously characterized an isolate that exhibited greater biofilm formation, aggregation and oyster colonization than its parent. This was due, in part, to the production of a Type IV Tad pilus (Iam). However, the locus lacked key processing and regulatory genes required for pilus production. Here, we identify a pilin peptidase iamP, and LysR-type regulator (LRTR) iamR, that fulfil these roles and show that environmental calcium, which oysters enrich for shell repair and growth, regulates iam expression. The architecture of the iam locus differs from the classical LRTR paradigm and requires an additional promoter to be integrated into the regulatory network. IamR specifically recognized the iamR promoter (PiamR ) and the intergenic iamP-iamA region (PiamP-A ). PiamR exhibited classical negative auto-regulation but, strikingly, IamR inversely regulated the divergent iamP and iamA promoters in a calcium-dependent manner. Moreover, expression of the c-di-GMP and calcium-regulated, biofilm-promoting brp exopolysaccharide was IamA-dependent. These results support a scenario in which the calcium-enriched oyster environment triggers IamP-mediated processing of prepilin amassed in the periplasm for rapid pilin elaboration and subsequent BRP production to promote colonization.
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Affiliation(s)
- Meng Pu
- Department of Biology, Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Emily Storms
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Dan M Chodur
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Dean A Rowe-Magnus
- Department of Biology, Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA.,Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
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15
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Petersen A, Crocoll C, Halkier BA. De novo production of benzyl glucosinolate in Escherichia coli. Metab Eng 2019; 54:24-34. [DOI: 10.1016/j.ymben.2019.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/11/2019] [Accepted: 02/24/2019] [Indexed: 12/30/2022]
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16
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Dong J, Chen Y, Benites VT, Baidoo EEK, Petzold CJ, Beller HR, Eudes A, Scheller HV, Adams PD, Mukhopadhyay A, Simmons BA, Singer SW. Methyl ketone production by Pseudomonas putida is enhanced by plant-derived amino acids. Biotechnol Bioeng 2019; 116:1909-1922. [PMID: 30982958 DOI: 10.1002/bit.26995] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/13/2019] [Accepted: 04/11/2019] [Indexed: 01/08/2023]
Abstract
Plants are an attractive sourceof renewable carbon for conversion to biofuels and bio-based chemicals. Conversion strategies often use a fraction of the biomass, focusing on sugars from cellulose and hemicellulose. Strategies that use plant components, such as aromatics and amino acids, may improve the efficiency of biomass conversion. Pseudomonas putida is a promising host for its ability to metabolize a wide variety of organic compounds. P. putida was engineered to produce methyl ketones, which are promising diesel blendstocks and potential platform chemicals, from glucose and lignin-related aromatics. Unexpectedly, P. putida methyl ketone production using Arabidopsis thaliana hydrolysates was enhanced 2-5-fold compared with sugar controls derived from engineered plants that overproduce lignin-related aromatics. This enhancement was more pronounced (~seven-fold increase) with hydrolysates from nonengineered switchgrass. Proteomic analysis of the methyl ketone-producing P. putida suggested that plant-derived amino acids may be the source of this enhancement. Mass spectrometry-based measurements of plant-derived amino acids demonstrated a high correlation between methyl ketone production and amino acid concentration in plant hydrolysates. Amendment of glucose-containing minimal media with a defined mixture of amino acids similar to those found in the hydrolysates studied led to a nine-fold increase in methyl ketone titer (1.1 g/L).
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Affiliation(s)
- Jie Dong
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Yan Chen
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Veronica Teixeira Benites
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Edward E K Baidoo
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Christopher J Petzold
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Harry R Beller
- Joint BioEnergy Institute, Emeryville, California.,Earth and Environmental Sciences, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Aymerick Eudes
- Joint BioEnergy Institute, Emeryville, California.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Henrik V Scheller
- Joint BioEnergy Institute, Emeryville, California.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Paul D Adams
- Joint BioEnergy Institute, Emeryville, California.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Aindrila Mukhopadhyay
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Blake A Simmons
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Steven W Singer
- Joint BioEnergy Institute, Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
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17
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Faramarzi T, Mobasheri M, Yoosefy A, Valadkhani Z. Expression and purification of truncated recombinant B8/1 protein of Echinococcus granulosus for diagnosis of hydatid infection in human. Acta Trop 2019; 191:139-145. [PMID: 30599175 DOI: 10.1016/j.actatropica.2018.12.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 12/04/2018] [Accepted: 12/28/2018] [Indexed: 12/28/2022]
Abstract
Hydatidosis is one of the most important diseases common between animals and human beings. Caused by Echinococcus granulosus tapeworm, the disease has a global epidemic. The serological diagnostic tests that are now utilized to confirm the imaging approaches have some drawbacks such as low sensitivity and cross-reaction with the serum of the patients infected with other parasites. The application of recombinant and synthetic antigens has proven improvement in the functionality of serological diagnostic tests. The purpose of this study was to demonstrate the expression and purification of truncated recombinant B8/1 (trB8/1) antigen and its application in ELISA for diagnosis of hydatid infection in human. The tEgB8/1 was colonized in the expression vector pET28b (+) and expressed in different strains of E. coli. This protein was purified by Ni2+-NTA chromatography. The antigenicity of the protein was evaluated by Western blotting and ELISA. In the test, 50 positive serum samples from hydatid infected patients, 50 samples from healthy people, and 30 serum samples from patients with other parasitic diseases were used to determine the sensitivity and the specificity of this antigen. The measured sensitivity and specificity of this antigen were identified to be 75.75% and 96.38% respectively. The P value of <0.0001 by using ROC curve, confirmed that this antigen is able to differentiate between healthy and hydatid-infected individuals. Considering the excellent specificity of this antigen and in order to enhance the sensitivity, it is recommended to use a combination of this antigen with other antigens (e.g., EgB8/2-8/5).
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Affiliation(s)
- Tahereh Faramarzi
- Department of Biotechnology, Faculty of Advanced Sciences and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran; Department of Parasitology, Pasteur Institute of Iran, Tehran, Iran
| | - Meysam Mobasheri
- Department of Biotechnology, Faculty of Advanced Sciences and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
| | - Asiyeh Yoosefy
- Department of Parasitology, Pasteur Institute of Iran, Tehran, Iran
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18
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Choudhury D, Gayen K, Saini S. Dynamic control of arabinose and xylose utilization in E. coli. CAN J CHEM ENG 2018. [DOI: 10.1002/cjce.23197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Debika Choudhury
- Department of Chemical Engineering; IIT Bombay; Mumbai Maharashtra 400076 India
| | - Kalyan Gayen
- Department of Chemical Engineering; NIT Agartala; Tripura 799055 India
| | - Supreet Saini
- Department of Chemical Engineering; IIT Bombay; Mumbai Maharashtra 400076 India
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19
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Monteiro LMO, Arruda LM, Silva-Rocha R. Emergent Properties in Complex Synthetic Bacterial Promoters. ACS Synth Biol 2018; 7:602-612. [PMID: 29091423 DOI: 10.1021/acssynbio.7b00344] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Regulation of gene expression in bacteria results from the interplay between hundreds of transcriptional factors (TFs) at target promoters. However, how the arrangement of binding sites for TFs generates the regulatory logic of promoters is not well-known. Here, we generated and fully characterized a library of synthetic complex promoters for the global regulators, CRP and IHF, in Escherichia coli, which are formed by a weak -35/-10 consensus sequence preceded by four combinatorial binding sites for these two TFs. Using this approach, we found that while cis-elements for CRP preferentially activate promoters when located immediately upstream of the promoter consensus, binding sites for IHF mainly function as "UP" elements and stimulate transcription in several different architectures in the absence of this protein. However, the combination of CRP- and IHF-binding sites resulted in emergent properties in these complex promoters, where the activity of combinatorial promoters cannot be predicted from the individual behavior of its components. Taken together, the results presented here add to the information on architecture-logic of complex promoters in bacteria.
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Affiliation(s)
- Lummy Maria Oliveira Monteiro
- Systems and Synthetic Biology Lab,
Ribeirao Preto Medical School, University of São Paulo, Ribeirão
Preto, São Paulo, Brazil
| | - Letícia Magalhães Arruda
- Systems and Synthetic Biology Lab,
Ribeirao Preto Medical School, University of São Paulo, Ribeirão
Preto, São Paulo, Brazil
| | - Rafael Silva-Rocha
- Systems and Synthetic Biology Lab,
Ribeirao Preto Medical School, University of São Paulo, Ribeirão
Preto, São Paulo, Brazil
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20
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Immethun CM, DeLorenzo DM, Focht CM, Gupta D, Johnson CB, Moon TS. Physical, chemical, and metabolic state sensors expand the synthetic biology toolbox for Synechocystis sp. PCC 6803. Biotechnol Bioeng 2017; 114:1561-1569. [PMID: 28244586 DOI: 10.1002/bit.26275] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 01/19/2017] [Accepted: 02/19/2017] [Indexed: 02/04/2023]
Abstract
Many under-developed organisms possess important traits that can boost the effectiveness and sustainability of microbial biotechnology. Photoautotrophic cyanobacteria can utilize the energy captured from light to fix carbon dioxide for their metabolic needs while living in environments not suited for growing crops. Various value-added compounds have been produced by cyanobacteria in the laboratory; yet, the products' titers and yields are often not industrially relevant and lag behind what have been accomplished in heterotrophic microbes. Genetic tools for biological process control are needed to take advantage of cyanobacteria's beneficial qualities, as tool development also lags behind what has been created in common heterotrophic hosts. To address this problem, we developed a suite of sensors that regulate transcription in the model cyanobacterium Synechocystis sp. PCC 6803 in response to metabolically relevant signals, including light and the cell's nitrogen status, and a family of sensors that respond to the inexpensive chemical, l-arabinose. Increasing the number of available tools enables more complex and precise control of gene expression. Expanding the synthetic biology toolbox for this cyanobacterium also improves our ability to utilize this important under-developed organism in biotechnology. Biotechnol. Bioeng. 2017;114: 1561-1569. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Cheryl M Immethun
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Drew M DeLorenzo
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Caroline M Focht
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Dinesh Gupta
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Charles B Johnson
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Tae Seok Moon
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
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21
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Marschall L, Sagmeister P, Herwig C. Tunable recombinant protein expression in E. coli: promoter systems and genetic constraints. Appl Microbiol Biotechnol 2017; 101:501-512. [PMID: 27999902 PMCID: PMC5566544 DOI: 10.1007/s00253-016-8045-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Revised: 11/26/2016] [Accepted: 11/29/2016] [Indexed: 12/11/2022]
Abstract
Tuning of transcription is a promising strategy to overcome challenges associated with a non-suitable expression rate like outgrowth of segregants, inclusion body formation, metabolic burden and inefficient translocation. By adjusting the expression rate-even on line-to purposeful levels higher product titres and more cost-efficient production processes can be achieved by enabling culture long-term stability and constant product quality. Some tunable systems are registered for patents or already commercially available. Within this contribution, we discuss the induction mechanisms of various Escherichia coli inherent promoter systems with respect to their tunability and review studies using these systems for expression tuning. According to the current level of knowledge, some promoter systems were successfully used for expression tuning, and in some cases, analytical evidence on single-cell level is still pending. However, only a few studies using tunable strains apply a suitable process control strategy. So far, expression tuning has only gathered little attention, but we anticipate that expression tuning harbours great potential for enabling and optimizing the production of a broad spectrum of products in E. coli.
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Affiliation(s)
- Lukas Marschall
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Vienna University of Technology, Vienna, Austria
| | | | - Christoph Herwig
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Vienna University of Technology, Vienna, Austria.
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Gumpendorferstrasse 1a/166-4, A-1060, Vienna, Austria.
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22
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The Escherichia coli rhaSR-PrhaBAD Inducible Promoter System Allows Tightly Controlled Gene Expression over a Wide Range in Pseudomonas aeruginosa. Appl Environ Microbiol 2016; 82:6715-6727. [PMID: 27613678 DOI: 10.1128/aem.02041-16] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/01/2016] [Indexed: 12/31/2022] Open
Abstract
The araC-ParaBAD inducible promoter system is tightly controlled and allows gene expression to be modulated over a wide range in Escherichia coli, which has led to its widespread use in other bacteria. Although anecdotal evidence suggests that araC-ParaBAD is leaky in Pseudomonas aeruginosa, neither a thorough analysis of this inducible promoter system in P. aeruginosa nor a concerted effort to identify alternatives with improved functionality has been reported. Here, we evaluated the functionality of the araC-ParaBAD system in P. aeruginosa Using transcriptional fusions to a lacZ reporter gene, we determined that the noninduced expression from araC-ParaBAD is high and cannot be reduced by carbon catabolite repression as it can in E. coli Modulating translational initiation by altering ribosome-binding site strength reduced the noninduced activity but also decreased the maximal induced activity and narrowed the induction range. Integrating the inducible promoter system into the posttranscriptional regulatory network that controls catabolite repression in P. aeruginosa significantly decreased the noninduced activity and increased the induction range. In addition to these improvements in the functionality of the araC-ParaBAD system, we found that the lacIq-Ptac and rhaSR-PrhaBAD inducible promoter systems had significantly lower noninduced expression and were inducible over a broader range than araC-ParaBAD We demonstrated that noninduced expression from the araC-ParaBAD system supported the function of genes involved in antibiotic resistance and tryptophan biosynthesis in P. aeruginosa, problems that were avoided with rhaSR-PrhaBAD. rhaSR-PrhaBAD is tightly controlled, allows gene expression over a wide range, and represents a significant improvement over araC-ParaBAD in P. aeruginosa IMPORTANCE: We report the shortcomings of the commonly used Escherichia coli araC-ParaBAD inducible promoter system in Pseudomonas aeruginosa, successfully reengineered it to improve its functionality, and show that the E. coli rhaSR-PrhaBAD system is tightly controlled and allows inducible gene expression over a wide range in P. aeruginosa.
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23
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Dharmasena MN, Feuille CM, Starke CEC, Bhagwat AA, Stibitz S, Kopecko DJ. Development of an Acid-Resistant Salmonella Typhi Ty21a Attenuated Vector For Improved Oral Vaccine Delivery. PLoS One 2016; 11:e0163511. [PMID: 27673328 PMCID: PMC5046385 DOI: 10.1371/journal.pone.0163511] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 09/09/2016] [Indexed: 02/01/2023] Open
Abstract
The licensed oral, live-attenuated bacterial vaccine for typhoid fever, Salmonella enterica serovar Typhi strain Ty21a, has also been utilized as a vaccine delivery platform for expression of diverse foreign antigens that stimulate protection against shigellosis, anthrax, plague, or human papilloma virus. However, Ty21a is acid-labile and, for effective oral immunization, stomach acidity has to be either neutralized with buffer or by-passed with Ty21a in an enteric-coated capsule (ECC). Several studies have shown that efficacy is reduced when Ty21a is administered in an ECC versus as a buffered liquid formulation, the former limiting exposure to GI tract lymphoid tissues. However, the ECC was selected as a more practical delivery format for both packaging/shipping and vaccine administration ease. We have sought to increase Ty21a acid-resistance to allow for removal from the ECC and immune enhancement. To improve Ty21a acid-resistance, glutamate-dependent acid resistance genes (GAD; responsible for Shigella spp. survival at very low pH) were cloned on a multi-copy plasmid (pGad) under a controllable arabinose-inducible promoter. pGad enhanced acid survival of Ty21a by 5 logs after 3 hours at pH 2.5, when cells were pre-grown in arabinose and under conditions that promote an acid-tolerance response (ATR). For genetically 100% stable expression, we inserted the gad genes into the Ty21a chromosome, using a method that allowed for subsequent removal of a selectable antibiotic resistance marker. Further, both bacterial growth curves and survival assays in cultured human monocytes/macrophages suggest that neither the genetic methods employed nor the resulting acid-resistance conferred by expression of the Gad proteins in Ty21a had any effect on the existing attenuation of this vaccine strain.
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Affiliation(s)
- Madushini N. Dharmasena
- Laboratory of Mucosal Pathogens and Cellular Immunology, Food and Drug Administration-Center for Biologics Evaluation and Research, New Hampshire Avenue, Silver Spring, Maryland, United States of America
- * E-mail: (MND); (DJK)
| | - Catherine M. Feuille
- Laboratory of Mucosal Pathogens and Cellular Immunology, Food and Drug Administration-Center for Biologics Evaluation and Research, New Hampshire Avenue, Silver Spring, Maryland, United States of America
| | - Carly Elizabeth C. Starke
- Laboratory of Mucosal Pathogens and Cellular Immunology, Food and Drug Administration-Center for Biologics Evaluation and Research, New Hampshire Avenue, Silver Spring, Maryland, United States of America
| | - Arvind A. Bhagwat
- Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland, United States of America
| | - Scott Stibitz
- Laboratory of Mucosal Pathogens and Cellular Immunology, Food and Drug Administration-Center for Biologics Evaluation and Research, New Hampshire Avenue, Silver Spring, Maryland, United States of America
| | - Dennis J. Kopecko
- Laboratory of Mucosal Pathogens and Cellular Immunology, Food and Drug Administration-Center for Biologics Evaluation and Research, New Hampshire Avenue, Silver Spring, Maryland, United States of America
- * E-mail: (MND); (DJK)
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24
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Gholizadeh M, Khanahmad H, Memarnejadian A, Aghasadeghi MR, Roohvand F, Sadat SM, Cohan RA, Nazemi A, Motevalli F, Asgary V, Arezumand R. Design and expression of fusion protein consists of HBsAg and Polyepitope of HCV as an HCV potential vaccine. Adv Biomed Res 2015; 4:243. [PMID: 26682209 PMCID: PMC4673707 DOI: 10.4103/2277-9175.168610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 03/16/2015] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Hepatitis C virus (HCV) infection is a serious public health threat worldwide. Cellular immune responses, especially cytotoxic T-lymphocytes (CTLs), play a critical role in immune response toward the HCV clearance. Since polytope vaccines have the ability to stimulate the cellular immunity, a recombinant fusion protein was developed in this study. MATERIALS AND METHODS The designed fusion protein is composed of hepatitis B surface antigen (HBsAg), as an immunocarrier, fused to an HCV polytope sequence. The polytope containing five immunogenic epitopes of HCV was designed to induce specific CTL responses. The construct was cloned into the pET-28a, and its expression was investigated in BL21 (DE3), BL21 pLysS, BL21 pLysE, and BL21 AI Escherichia coli strains using 12% gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Finally, the identity of expressed fusion protein was confirmed by Western blotting using anti-His monoclonal antibody and affinity chromatography was applied to purify the expressed protein. RESULTS The accuracy of the construct was confirmed by restriction map analysis and sequencing. The transformation of the construct into the BL21 (DE3), pLysS, and pLysE E. coli strains did not lead to any expression. The fusion protein was found to be toxic for E. coli DE3. By applying two steps inhibition, the fusion protein was successfully expressed in BL21 (AI) E. coli strain. CONCLUSION The HBsAg-polytope fusion protein expressed in this study can be further evaluated for its immunogenicity in animal models.
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Affiliation(s)
- Monireh Gholizadeh
- Department of Biology, Islamic Azad University, Tonekabon Branch, Tonekabon, Iran
| | - Hossein Khanahmad
- Department of Genetics, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | | | | | - Farzin Roohvand
- Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran, Iran
| | - Seyed Mehdi Sadat
- Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran, Iran
| | | | - Ali Nazemi
- Department of Biology, Islamic Azad University, Tonekabon Branch, Tonekabon, Iran
| | - Fatemeh Motevalli
- Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran, Iran
| | - Vahid Asgary
- Department Of Rabies, Pasteur Institute of Iran, Tehran, Iran ; Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Roghaye Arezumand
- Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
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Hong H, Lim D, Kim GJ, Park SH, Sik Kim H, Hong Y, Choy HE, Min JJ. Targeted deletion of the ara operon of Salmonella typhimurium enhances L-arabinose accumulation and drives PBAD-promoted expression of anti-cancer toxins and imaging agents. Cell Cycle 2015; 13:3112-20. [PMID: 25486570 DOI: 10.4161/15384101.2014.949527] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Tumor-specific expression of antitumor drugs can be achieved using attenuated Salmonella typhimurium harboring the PBAD promoter, which is induced by L-arabinose. However, L-arabinose does not accumulate because it is metabolized to D-xylulose-5-P by enzymes encoded by the ara operon in Salmonellae. To address this problem, we developed an engineered strain of S. typhimurium in which the ara operon is deleted. Linear DNA transformation was performed using λ red recombinase to exchange the ara operon with linear DNA carrying an antibiotic-resistance gene with homology to regions adjacent to the ara operon. The ara operon-deleted strain and its parental strain were transformed with a plasmid encoding Renilla luciferase variant 8 (RLuc8) or cytolysin A (clyA) under the control of the PBAD promoter. Luciferase assays demonstrated that RLuc8 expression was 49-fold higher in the ara operon-deleted S. typhimurium than in the parental strain after the addition of L-arabinose. In vivo bioluminescence imaging showed that the tumor tissue targeted by the ara operon-deleted Salmonella had a stronger imaging signal (~30-fold) than that targeted by the parental strain. Mice with murine colon cancer (CT26) that had been injected with the ara operon-deleted S. typhimurium expressing clyA showed significant tumor suppression. The present report demonstrates that deletion of the ara operon of S. typhimurium enhances L-arabinose accumulation and thereby drives PBAD-promoted expression of cytotoxic agents and imaging agents. This is a promising approach for tumor therapy and imaging.
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Affiliation(s)
- Hyun Hong
- a Department of Nuclear Medicine ; Chonnam National University Medical School and Hwasun Hospital ; Jeonnam , Republic of Korea
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Tran H, Oliveira SMD, Goncalves N, Ribeiro AS. Kinetics of the cellular intake of a gene expression inducer at high concentrations. MOLECULAR BIOSYSTEMS 2015. [PMID: 26223179 DOI: 10.1039/c5mb00244c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
From in vivo single-event measurements of the transient and steady-state transcription activity of a single-copy lac-ara-1 promoter in Escherichia coli, we characterize the intake kinetics of its inducer (IPTG) from the media. We show that the empirical data are well-fit by a model of intake assuming a bilayer membrane, with the passage through the second layer being rate-limiting, coupled to a stochastic, sub-Poissonian, multi-step transcription process. Using this model, we show that for a wide range of extracellular inducer levels (up to 1.25 mM) the intake process is diffusive-like, suggesting unsaturated membrane permeability. Inducer molecules travel from the periplasm to the cytoplasm in, on average, 31.7 minutes, strongly affecting cells' response time. The novel methodology followed here should aid the study of cellular intake mechanisms at the single-event level.
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Affiliation(s)
- Huy Tran
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, FI-33101 Tampere, Finland.
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Amouyal M. From adjacent activation in Escherichia coli and DNA cyclization to eukaryotic enhancers: the elements of a puzzle. Front Genet 2014; 5:371. [PMID: 25404937 PMCID: PMC4217526 DOI: 10.3389/fgene.2014.00371] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 10/04/2014] [Indexed: 11/13/2022] Open
Abstract
Deoxyribonucleic acid cyclization, Escherichia coli lac repressor binding to two spaced lac operators and repression enhancement can be successfully used for a better understanding of the conditions required for interaction between eukaryotic enhancers and the machinery of transcription initiation. Chronologically, the DNA looping model has first accounted for the properties initially defining enhancers, i.e., independence of action with distance or orientation with respect to the start of transcription. It has also predicted enhancer activity or its disruption at short distance (site orientation, alignment between promoter and enhancer sites), with high-order complexes of protein, or with transcription factor concentrations close or different from the wild-type situation. In another step, histones have been introduced into the model to further adapt it to eukaryotes. They in fact favor DNA cyclization in vitro. The resulting DNA compaction might explain the difference counted in base pairs in the distance of action between eukaryotic transcription enhancers and prokaryotic repression enhancers. The lac looping system provides a potential tool for analysis of this discrepancy and of chromatin state directly in situ. Furthermore, as predicted by the model, the contribution of operators O2 and O3 to repression of the lac operon clearly depends on the lac repressor level in the cell and is prevented in strains overproducing lac repressor. By extension, gene regulation especially that linked to cell fate, should also depend on transcription factor levels, providing a potential tool for cellular therapy. In parallel, a new function of the O1–O3 loop completes the picture of lac repression. The O1–O3 loop would at the same time ensure high efficiency of repression, inducibility through the low-affinity sites and limitation of the level of repressor through self-repression of the lac repressor. Last, the DNA looping model can be successfully adapted to the enhancer auxiliary elements known as insulators.
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Affiliation(s)
- Michèle Amouyal
- Interactions à Distance, Centre National de la Recherche Scientifique Paris, France
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Raghavan V, Lowe EC, Townsend GE, Bolam DN, Groisman EA. Tuning transcription of nutrient utilization genes to catabolic rate promotes growth in a gut bacterium. Mol Microbiol 2014; 93:1010-25. [PMID: 25041429 DOI: 10.1111/mmi.12714] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2014] [Indexed: 01/30/2023]
Abstract
Cells respond to nutrient availability by expressing nutrient catabolic genes. We report that the regulator controlling utilization of chondroitin sulphate (CS) in the mammalian gut symbiont Bacteroides thetaiotaomicron is activated by an intermediate in CS breakdown rather than CS itself. We determine that the rate-determining enzyme in CS breakdown is responsible for degrading this intermediate and establish that the levels of the enzyme increase 100-fold, whereas those of the regulator remain constant upon exposure to CS. Because enzyme and regulator compete for the intermediate, B. thetaiotaomicron tunes transcription of CS utilization genes to CS catabolic rate. This tuning results in a transient increase in CS utilization transcripts upon exposure to excess CS. Constitutive expression of the rate-determining enzyme hindered activation of CS utilization genes and growth on CS. An analogous mechanism regulates heparin utilization genes, suggesting that the identified strategy aids B. thetaiotaomicron in the competitive gut environment.
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Affiliation(s)
- Varsha Raghavan
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, 63105, USA
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Mund M, Overbeck JH, Ullmann J, Sprangers R. LEGO-NMR: eine Methode zur Visualisierung einzelner Untereinheiten in großen heteromeren Komplexen. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201304914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mund M, Overbeck JH, Ullmann J, Sprangers R. LEGO-NMR spectroscopy: a method to visualize individual subunits in large heteromeric complexes. Angew Chem Int Ed Engl 2013; 52:11401-5. [PMID: 23946163 PMCID: PMC4138990 DOI: 10.1002/anie.201304914] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Indexed: 11/10/2022]
Abstract
Seeing the big picture: Asymmetric macromolecular complexes that are NMR active in only a subset of their subunits can be prepared, thus decreasing NMR spectral complexity. For the hetero heptameric LSm1-7 and LSm2-8 rings NMR spectra of the individual subunits of the complete complex are obtained, showing a conserved RNA binding site. This LEGO-NMR technique makes large asymmetric complexes accessible to detailed NMR spectroscopic studies.
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Affiliation(s)
- Markus Mund
- Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen (Germany); Present address: European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg (Germany)
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Topological plasticity of enzymes involved in disulfide bond formation allows catalysis in either the periplasm or the cytoplasm. J Mol Biol 2013; 425:3268-76. [PMID: 23810903 DOI: 10.1016/j.jmb.2013.04.034] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 11/23/2022]
Abstract
The transmembrane enzymes disulfide bond forming enzyme B (DsbB) and vitamin K epoxide reductase (VKOR) are central to oxidative protein folding in the periplasm of prokaryotes. Catalyzed formation of structural disulfide bonds in proteins also occurs in the cytoplasm of some hyperthermophilic prokaryotes through currently, poorly defined mechanisms. We aimed to determine whether DsbB and VKOR can be inverted in the membrane with retention of activity. By rational design of inversion of membrane topology, we engineered DsbB mutants that catalyze disulfide bond formation in the cytoplasm of Escherichia coli. This represents the first engineered inversion of a transmembrane protein with demonstrated conservation of activity and substrate specificity. This successful designed engineering led us to identify two naturally occurring and oppositely oriented VKOR homologues from the hyperthermophile Aeropyrum pernix that promote oxidative protein folding in the periplasm or cytoplasm, respectively, and hence defines the probable route for disulfide bond formation in the cytoplasm of hyperthermophiles. Our findings demonstrate how knowledge on the determinants of membrane protein topology can be used to de novo engineer a metabolic pathway and to unravel an intriguingly simple evolutionary scenario where a new "adaptive" cellular process is constructed by means of membrane protein topology inversion.
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Shimada T, Kori A, Ishihama A. Involvement of the ribose operon repressor RbsR in regulation of purine nucleotide synthesis in Escherichia coli. FEMS Microbiol Lett 2013; 344:159-65. [PMID: 23651393 DOI: 10.1111/1574-6968.12172] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 05/02/2013] [Accepted: 05/02/2013] [Indexed: 01/04/2023] Open
Abstract
Escherichia coli is able to utilize d-ribose as its sole carbon source. The genes for the transport and initial-step metabolism of d-ribose form a single rbsDACBK operon. RbsABC forms the ABC-type high-affinity d-ribose transporter, while RbsD and RbsK are involved in the conversion of d-ribose into d-ribose 5-phosphate. In the absence of inducer d-ribose, the ribose operon is repressed by a LacI-type transcription factor RbsR, which is encoded by a gene located downstream of this ribose operon. At present, the rbs operon is believed to be the only target of regulation by RbsR. After Genomic SELEX screening, however, we have identified that RbsR binds not only to the rbs promoter but also to the promoters of a set of genes involved in purine nucleotide metabolism. Northern blotting analysis indicated that RbsR represses the purHD operon for de novo synthesis of purine nucleotide but activates the add and udk genes involved in the salvage pathway of purine nucleotide synthesis. Taken together, we propose that RbsR is a global regulator for switch control between the de novo synthesis of purine nucleotides and its salvage pathway.
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Affiliation(s)
- Tomohiro Shimada
- Department of Frontier Bioscience, Hosei University, Koganei, Tokyo, Japan
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Balzer S, Kucharova V, Megerle J, Lale R, Brautaset T, Valla S. A comparative analysis of the properties of regulated promoter systems commonly used for recombinant gene expression in Escherichia coli. Microb Cell Fact 2013; 12:26. [PMID: 23506076 PMCID: PMC3621392 DOI: 10.1186/1475-2859-12-26] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 03/01/2013] [Indexed: 11/20/2022] Open
Abstract
Background Production of recombinant proteins in bacteria for academic and commercial purposes is a well established field; however the outcomes of process developments for specific proteins are still often unpredictable. One reason is the limited understanding of the performance of expression cassettes relative to each other due to different genetic contexts. Here we report the results of a systematic study aiming at exclusively comparing commonly used regulator/promoter systems by standardizing the designs of the replicon backbones. Results The vectors used in this study are based on either the RK2- or the pMB1- origin of replication and contain the regulator/promoter regions of XylS/Pm (wild-type), XylS/Pm ML1-17 (a Pm variant), LacI/PT7lac, LacI/Ptrc and AraC/PBAD to control expression of different proteins with various origins. Generally and not unexpected high expression levels correlate with high replicon copy number and the LacI/PT7lac system generates more transcript than all the four other cassettes. However, this transcriptional feature does not always lead to a correspondingly more efficient protein production, particularly if protein functionality is considered. In most cases the XylS/Pm ML1-17 and LacI/PT7lac systems gave rise to the highest amounts of functional protein production, and the XylS/Pm ML1-17 is the most flexible in the sense that it does not require any specific features of the host. The AraC/PBAD system is very good with respect to tightness, and a commonly used bioinformatics prediction tool (RBS calculator) suggested that it has the most translation-efficient UTR. Expression was also studied by flow cytometry in individual cells, and the results indicate that cell to cell heterogeneity is very relevant for understanding protein production at the population level. Conclusions The choice of expression system needs to be evaluated for each specific case, but we believe that the standardized vectors developed for this study can be used to more easily identify the nature of case-specific bottlenecks. By then taking into account the relevant characteristics of each expression cassette it will be easier to make the best choice with respect to the goal of achieving high levels of protein expression in functional or non-functional form.
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Affiliation(s)
- Simone Balzer
- Department of Biotechnology, NTNU, Sem Sælands vei 6, Trondheim 7491, Norway
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Fieseler L, Schmitter S, Teiserskas J, Loessner MJ. Rhamnose-inducible gene expression in Listeria monocytogenes. PLoS One 2012; 7:e43444. [PMID: 22927968 PMCID: PMC3425472 DOI: 10.1371/journal.pone.0043444] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 07/20/2012] [Indexed: 12/02/2022] Open
Abstract
Acid production from rhamnose is a characteristic phenotype of Listeria monocytogenes. We report the identification of the rhamnose transport and utilization operon located at lmo2846 to lmo2851, including the rhamnose-dependent promoter Prha. Expression of reporter genes under control of Prha on a single copy integration vector demonstrated its suitability for inducible gene expression in L. monocytogenes. Transcription initiation from Prha is dose dependent, and a concentration as low as 100 µM rhamnose was found sufficient for induction. Moreover, Prha is subject to glucose catabolite repression, which provides additional options for strict control of expression. Infection of human THP1 macrophages revealed that Prha is repressed in intracellular L. monocytogenes, which is explained by the absence of rhamnose in the cytosol and possible interference by catabolite repression. The Prha promoter provides a novel and useful tool for triggering gene expression in extracellular L. monocytogenes, whereas intracellular conditions prevent transcription from this promoter.
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Affiliation(s)
- Lars Fieseler
- Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland
| | - Sibylle Schmitter
- Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland
| | | | - Martin J. Loessner
- Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland
- * E-mail:
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Development and application of an arabinose-inducible expression system by facilitating inducer uptake in Corynebacterium glutamicum. Appl Environ Microbiol 2012; 78:5831-8. [PMID: 22685153 DOI: 10.1128/aem.01147-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium glutamicum is currently used for the industrial production of a variety of biological materials. Many available inducible expression systems in this species use lac-derived promoters from Escherichia coli that exhibit much lower levels of inducible expression and leaky basal expression. We developed an arabinose-inducible expression system that contains the L-arabinose regulator AraC, the P(BAD) promoter from the araBAD operon, and the L-arabinose transporter AraE, all of which are derived from E. coli. The level of inducible P(BAD)-based expression could be modulated over a wide concentration range from 0.001 to 0.4% L-arabinose. This system tightly controlled the expression of the uracil phosphoribosyltransferase without leaky expression. When the gene encoding green fluorescent protein (GFP) was under the control of P(BAD) promoter, flow cytometry analysis showed that GFP was expressed in a highly homogeneous profile throughout the cell population. In contrast to the case in E. coli, P(BAD) induction was not significantly affected in the presence of different carbon sources in C. glutamicum, which makes it useful in fermentation applications. We used this system to regulate the expression of the odhI gene from C. glutamicum, which encodes an inhibitor of α-oxoglutarate dehydrogenase, resulting in high levels of glutamate production (up to 13.7 mM) under biotin nonlimiting conditions. This system provides an efficient tool available for molecular biology and metabolic engineering of C. glutamicum.
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Lambda red-mediated genetic modification of the insect endosymbiont Sodalis glossinidius. Appl Environ Microbiol 2011; 77:1918-20. [PMID: 21216910 DOI: 10.1128/aem.02166-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the current study, we adapted and optimized the lambda Red recombineering strategy to genetically manipulate the fastidious insect endosymbiont Sodalis glossinidius. This work greatly facilitates the application of genetics to the study of insect symbionts and should also prove useful in the context of long-awaited paratransgenic insect control strategies.
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Francis DM, Page R. Strategies to optimize protein expression in E. coli. CURRENT PROTOCOLS IN PROTEIN SCIENCE 2010; Chapter 5:5.24.1-5.24.29. [PMID: 20814932 PMCID: PMC7162232 DOI: 10.1002/0471140864.ps0524s61] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Recombinant protein expression in Escherichia coli (E. coli) is simple, fast, inexpensive, and robust, with the expressed protein comprising up to 50 percent of the total cellular protein. However, it also has disadvantages. For example, the rapidity of bacterial protein expression often results in unfolded/misfolded proteins, especially for heterologous proteins that require longer times and/or molecular chaperones to fold correctly. In addition, the highly reductive environment of the bacterial cytosol and the inability of E. coli to perform several eukaryotic post-translational modifications results in the insoluble expression of proteins that require these modifications for folding and activity. Fortunately, multiple, novel reagents and techniques have been developed that allow for the efficient, soluble production of a diverse range of heterologous proteins in E. coli. This overview describes variables at each stage of a protein expression experiment that can influence solubility and offers a summary of strategies used to optimize soluble expression in E. coli.
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Davidson CJ, Narang A, Surette MG. Integration of transcriptional inputs at promoters of the arabinose catabolic pathway. BMC SYSTEMS BIOLOGY 2010; 4:75. [PMID: 20525212 PMCID: PMC2893085 DOI: 10.1186/1752-0509-4-75] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Accepted: 06/02/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Most modelling efforts of transcriptional networks involve estimations of in vivo concentrations of components, binding affinities and reaction rates, derived from in vitro biochemical assays. These assays are difficult and in vitro measurements may not approximate actual in vivo conditions. Alternatively, changes in transcription factor activity can be estimated by using partially specified models which estimate the "hidden functions" of transcription factor concentration changes; however, non-unique solutions are a potential problem. We have applied a synthetic biology approach to develop reporters that are capable of measuring transcription factor activity in vivo in real time. These synthetic reporters are comprised of a constitutive promoter with an operator site for the specific transcription factor immediately downstream. Thus, increasing transcription factor activity is measured as repression of expression of the transcription factor reporter. Measuring repression instead of activation avoids the complications of non-linear interactions between the transcription factor and RNA polymerase which differs at each promoter. RESULTS Using these reporters, we show that a simple model is capable of determining the rules of integration for multiple transcriptional inputs at the four promoters of the arabinose catabolic pathway. Furthermore, we show that despite the complex and non-linear changes in cAMP-CRP activity in vivo during diauxic shift, the synthetic transcription factor reporters are capable of measuring real-time changes in transcription factor activity, and the simple model is capable of predicting the dynamic behaviour of the catabolic promoters. CONCLUSIONS Using a synthetic biology approach we show that the in vivo activity of transcription factors can be quantified without the need for measuring intracellular concentrations, binding affinities and reaction rates. Using measured transcription factor activity we show how different promoters can integrate common transcriptional inputs, resulting in distinct expression patterns. The data collected show that cAMP levels in vivo are dynamic and agree with observations showing that cAMP levels show a transient pulse during diauxic shift.
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Affiliation(s)
- Carla J Davidson
- University of Calgary, Department of Biology, BI376b 2500 University Dr. N.W., Calgary, AB. T2N 1N4 Canada
| | - Atul Narang
- Department of Biochemical Engineering & Biotechnology, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India
| | - Michael G Surette
- University of Calgary, Department of Microbiology and Infectious Diseases, Room 268 Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1 Canada
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Abstract
Regulated promoters are useful tools for many aspects related to recombinant gene expression in bacteria, including for high‐level expression of heterologous proteins and for expression at physiological levels in metabolic engineering applications. In general, it is common to express the genes of interest from an inducible promoter controlled either by a positive regulator or by a repressor protein. In this review, we discuss established and potentially useful positively regulated bacterial promoter systems, with a particular emphasis on those that are controlled by the AraC‐XylS family of transcriptional activators. The systems function in a wide range of microorganisms, including enterobacteria, soil bacteria, lactic bacteria and streptomycetes. The available systems that have been applied to express heterologous genes are regulated either by sugars (l‐arabinose, l‐rhamnose, xylose and sucrose), substituted benzenes, cyclohexanone‐related compounds, ε‐caprolactam, propionate, thiostrepton, alkanes or peptides. It is of applied interest that some of the inducers require the presence of transport systems, some are more prone than others to become metabolized by the host and some have been applied mainly in one or a limited number of species. Based on bioinformatics analyses, the AraC‐XylS family of regulators contains a large number of different members (currently over 300), but only a small fraction of these, the XylS/Pm, AraC/PBAD, RhaR‐RhaS/rhaBAD, NitR/PnitA and ChnR/Pb regulator/promoter systems, have so far been explored for biotechnological applications.
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Affiliation(s)
- Trygve Brautaset
- Department of Biotechnology, Sintef Materials and Chemistry, Sintef, Trondheim, Norway.
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Timing and dynamics of single cell gene expression in the arabinose utilization system. Biophys J 2008; 95:2103-15. [PMID: 18469087 DOI: 10.1529/biophysj.107.127191] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The arabinose utilization system of Escherichia coli displays a stochastic all-or-nothing response at intermediate levels of arabinose, where the population divides into a fraction catabolizing the sugar at a high rate (on-state) and a fraction not utilizing arabinose (off-state). Here we study this decision process in individual cells, focusing on the dynamics of the transition from the off- to the on-state. Using quantitative time-lapse microscopy, we determine the time delay between inducer addition and fluorescence onset of a GFP reporter. Through independent characterization of the GFP maturation process, we can separate the lag time caused by the reporter from the intrinsic activation time of the arabinose system. The resulting distribution of intrinsic time delays scales inversely with the external arabinose concentration, and is compatible with a simple stochastic model for arabinose uptake. Our findings support the idea that the heterogeneous timing of gene induction is causally related to a broad distribution of uptake proteins at the time of sugar addition.
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Construction and characterization of a recombinant whole-cell biocatalyst of Escherichia coli expressing styrene monooxygenase under the control of arabinose promoter. BIOTECHNOL BIOPROC E 2008. [DOI: 10.1007/s12257-007-0172-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Mruk I, Rajesh P, Blumenthal RM. Regulatory circuit based on autogenous activation-repression: roles of C-boxes and spacer sequences in control of the PvuII restriction-modification system. Nucleic Acids Res 2007; 35:6935-52. [PMID: 17933763 PMCID: PMC2175313 DOI: 10.1093/nar/gkm837] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Type II restriction-modification (R-M) systems comprise a restriction endonuclease (REase) and a protective methyltransferase (MTase). After R-M genes enter a new cell, MTase must appear before REase or the chromosome will be cleaved. PvuII and some other R-M systems achieve this delay by cotranscribing the REase gene with the gene for an autogenous transcription activator (the controlling or 'C' protein C.PvuII). This study reveals, through in vivo titration, that C.PvuII is not only an activator but also a repressor for its own gene. In other systems, this type of circuit can result in oscillatory behavior. Despite the use of identical, symmetrical C protein-binding sequences (C-boxes) in the left and right operators, C.PvuII showed higher in vitro affinity for O(L) than for O(R), implicating the spacer sequences in this difference. Mutational analysis associated the repression with O(R), which overlaps the promoter -35 hexamer but is otherwise dispensable for activation. A nonrepressing mutant exhibited poor establishment in new cells. Comparing promoter-operator regions from PvuII and 29 R-M systems controlled by C proteins revealed that the most-highly conserved sequence is the tetranucleotide spacer separating O(L) from O(R). Any changes in that spacer reduced the stability of C.PvuII-operator complexes and abolished activation.
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Affiliation(s)
- Iwona Mruk
- Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA
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44
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Semprini S, Troup T, Kotelevtseva N, King K, Davis J, Mullins L, Chapman K, Dunbar D, Mullins J. Cryptic loxP sites in mammalian genomes: genome-wide distribution and relevance for the efficiency of BAC/PAC recombineering techniques. Nucleic Acids Res 2007; 35:1402-10. [PMID: 17284462 PMCID: PMC1865043 DOI: 10.1093/nar/gkl1108] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cre is widely used for DNA tailoring and, in combination with recombineering techniques, to modify BAC/PAC sequences for generating transgenic animals. However, mammalian genomes contain recombinase recognition sites (cryptic loxP sites) that can promote illegitimate DNA recombination and damage when cells express the Cre recombinase gene. We have created a new bioinformatic tool, FuzznucComparator, which searches for cryptic loxP sites and we have applied it to the analysis of the whole mouse genome. We found that cryptic loxP sites occur frequently and are homogeneously distributed in the genome. Given the mammalian nature of BAC/PAC genomic inserts, we hypothesised that the presence of cryptic loxP sites may affect the ability to grow and modify BAC and PAC clones in E. coli expressing Cre recombinase. We have observed a defect in bacterial growth when some BACs and PACs were transformed into EL350, a DH10B-derived bacterial strain that expresses Cre recombinase under the control of an arabinose-inducible promoter. In this study, we have demonstrated that Cre recombinase expression is leaky in un-induced EL350 cells and that some BAC/PAC sequences contain cryptic loxP sites, which are active and mediate the introduction of single-strand nicks in BAC/PAC genomic inserts.
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Affiliation(s)
- S. Semprini
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - T.J. Troup
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - N. Kotelevtseva
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - K. King
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - J.R.E. Davis
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - L.J. Mullins
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - K.E. Chapman
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - D.R. Dunbar
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
| | - J.J. Mullins
- Molecular Physiology Group, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK, Current address: Department of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK, Endocrine Science Research Group, University of Manchester M13 9PT, UK and Endocrinology Unit, University of Edinburgh Medical School, Edinburgh EH16 4TJ, UK
- *To whom correspondence should be addressed. +44-131-242-6722+44-131-242-6782
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45
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Mdluli KE, Witte PR, Kline T, Barb AW, Erwin AL, Mansfield BE, McClerren AL, Pirrung MC, Tumey LN, Warrener P, Raetz CRH, Stover CK. Molecular validation of LpxC as an antibacterial drug target in Pseudomonas aeruginosa. Antimicrob Agents Chemother 2006; 50:2178-84. [PMID: 16723580 PMCID: PMC1479155 DOI: 10.1128/aac.00140-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
LpxC [UDP-3-O-(R-3-hydroxymyristoyl)-GlcNAc deacetylase] is a metalloamidase that catalyzes the first committed step in the biosynthesis of the lipid A component of lipopolysaccharide. A previous study (H. R. Onishi, B. A. Pelak, L. S. Gerckens, L. L. Silver, F. M. Kahan, M. H. Chen, A. A. Patchett, S. M. Galloway, S. A. Hyland, M. S. Anderson, and C. R. H. Raetz, Science 274:980-982, 1996) identified a series of synthetic LpxC-inhibitory molecules that were bactericidal for Escherichia coli. These molecules did not inhibit the growth of Pseudomonas aeruginosa and were therefore not developed further as antibacterial drugs. The inactivity of the LpxC inhibitors for P. aeruginosa raised the possibility that LpxC activity might not be essential for all gram-negative bacteria. By placing the lpxC gene of P. aeruginosa under tight control of an arabinose-inducible promoter, we demonstrated the essentiality of LpxC activity for P. aeruginosa. It was found that compound L-161,240, the most potent inhibitor from the previous study, was active against a P. aeruginosa construct in which the endogenous lpxC gene was inactivated and in which LpxC activity was supplied by the lpxC gene from E. coli. Conversely, an E. coli construct in which growth was dependent on the P. aeruginosa lpxC gene was resistant to the compound. The differential activities of L-161,240 against the two bacterial species are thus the result primarily of greater potency toward the E. coli enzyme rather than of differences in the intrinsic resistance of the bacteria toward antibacterial compounds due to permeability or efflux. These data validate P. aeruginosa LpxC as a target for novel antibiotic drugs and should help direct the design of inhibitors against clinically important gram-negative bacteria.
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Affiliation(s)
- Khisimuzi E Mdluli
- Department of Research Biology, Chiron Corporation, Seattle, WA 98119, USA
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46
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Chen Z, Zhao H. A highly sensitive selection method for directed evolution of homing endonucleases. Nucleic Acids Res 2005; 33:e154. [PMID: 16214805 PMCID: PMC1253837 DOI: 10.1093/nar/gni148] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Homing endonucleases are enzymes that catalyze DNA sequence specific double-strand breaks and can significantly stimulate homologous recombination at these breaks. These enzymes have great potential for applications such as gene correction in gene therapy or gene alteration in systems biology and metabolic engineering. However, homing endonucleases have a limited natural repertoire of target sequences, which severely hamper their applications. Here we report the development of a highly sensitive selection method for the directed evolution of homing endonucleases that couples enzymatic DNA cleavage with the survival of host cells. Using I-SceI as a model homing endonuclease, we have demonstrated that cells with wild-type I-SceI showed a high cell survival rate of 80–100% in the presence of the original I-SceI recognition site, whereas cells without I-SceI showed a survival rate <0.003%. This system should also be readily applicable for directed evolution of other DNA cleavage enzymes.
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Affiliation(s)
- Zhilei Chen
- Center for Biophysics and Computational Biology, University of IllinoisUrbana, IL 61801, USA
| | - Huimin Zhao
- Center for Biophysics and Computational Biology, University of IllinoisUrbana, IL 61801, USA
- Department of Chemical and Biomolecular Engineering, University of IllinoisUrbana, IL 61801, USA
- Department of Chemistry, University of IllinoisUrbana, IL 61801, USA
- Department of Bioengineering, University of IllinoisUrbana, IL 61801, USA
- Institute for Genomic Biology, University of IllinoisUrbana, IL 61801, USA
- To whom correspondence should be addressed. Tel: +1 217 333 2631; Fax: +1 217 333 5052;
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47
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Boomershine WP, Raj MLS, Gopalan V, Foster MP. Preparation of uniformly labeled NMR samples in Escherichia coli under the tight control of the araBAD promoter: expression of an archaeal homolog of the RNase P Rpp29 protein. Protein Expr Purif 2003; 28:246-51. [PMID: 12699688 DOI: 10.1016/s1046-5928(02)00707-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We report the first use of the tightly regulated araBAD promoter for generating uniformly labeled samples for NMR. The araBAD promoter provides a distinct advantage over that of the most commonly used protein overexpression systems in bacteria (e.g., in pET vectors: T7lac), in that it provides much tighter control over basal expression. However, use of araBAD-regulated expression for preparation of uniformly labeled protein samples for NMR is complicated by the fact that glucose (the most commonly used carbon source in defined minimal media) indirectly represses transcription, and thus, cannot be used. After experimenting with alternative media, we found that uniformly labeled NMR samples can be prepared using the highly regulated arabinose-inducible promoter and that suitable yields can be obtained in defined minimal media containing glycerol, not glucose, as the carbon source.
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48
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Lu C, Albano CR, Bentley WE, Rao G. Differential rates of gene expression monitored by green fluorescent protein. Biotechnol Bioeng 2002; 79:429-37. [PMID: 12115406 DOI: 10.1002/bit.10295] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The use of green fluorescent protein (GFP) as a reporter gene has made a broad impact in several areas, especially in studies of protein trafficking, localization, and expression analysis. GFP's many advantages are that it is small, autocatalytic, and does not require fixation, cell disruption, or the addition of cofactors or substrates. Two characteristics of GFP, extreme stability and chromophore cyclization lag time, pose a hindrance to the application of GFP as a real-time gene expression reporter in bioprocess applications. In this report, we present analytical methods that overcome these problems and enable the temporal visualization of discrete gene regulatory events. The approach we present measures the rate of change in GFP fluorescence, which in turn reflects the rate of gene expression. We conducted fermentation and microplate experiments using a protein synthesis inhibitor to illustrate the feasibility of this system. Additional experiments using the classic gene regulation of the araBAD operon show the utility of GFP as a near real-time indicator of gene regulation. With repetitive induction and repression of the arabinose promoter, the differential rate of GFP fluorescence emission shows corresponding cyclical changes during the culture.
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Affiliation(s)
- Canghai Lu
- Department of Chemical and Biochemical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, 21250, USA
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49
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Thapar N, Clarke S. Expression, purification, and characterization of the protein repair l-isoaspartyl methyltransferase from Arabidopsis thaliana. Protein Expr Purif 2000; 20:237-51. [PMID: 11049748 DOI: 10.1006/prep.2000.1311] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein l-isoaspartate (d-aspartate) O-methyltransferase (EC 2.1.1. 77) is a repair enzyme that methylates abnormal l-isoaspartate residues in proteins which arise spontaneously as a result of aging. This enzyme initiates their conversion back into the normal l-aspartate form by a methyl esterification reaction. Previously, partial cDNAs of this enzyme were isolated from the higher plant Arabidopsis thaliana. In this study, we report the cloning and expression of a full-length cDNA of l-isoaspartyl methyltransferase from A. thaliana into Escherichia coli under the P(BAD) promoter, which offers a high level of expression under a tight regulatory control. The enzyme is found largely in the soluble fraction. We purified this recombinant enzyme to homogeneity using a series of steps involving DEAE-cellulose, gel filtration, and hydrophobic interaction chromatographies. The homogeneous enzyme was found to have maximum activity at 45 degrees C and a pH optimum from 7 to 8. The enzyme was found to have a wide range of affinities for l-isoaspartate-containing peptides and displayed relatively poor reactivity toward protein substrates. The best methyl-accepting substrates were KASA-l-isoAsp-LAKY (K(m) = 80 microM) and VYP-l-isoAsp-HA (K(m) = 310 microM). We also expressed the full-length form and a truncated version of this enzyme (lacking the N-terminal 26 amino acid residues) in E. coli under the T7 promoter. Both the full-length and the truncated forms were active, though overexpression of the truncated enzyme led to a complete loss of activity.
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Affiliation(s)
- N Thapar
- Department of Chemistry and Biochemistry, Molecular Biology Institute, Los Angeles, California 90095, USA
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50
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Huang W, McKevitt M, Palzkill T. Use of the arabinose p(bad) promoter for tightly regulated display of proteins on bacteriophage. Gene 2000; 251:187-97. [PMID: 10876095 DOI: 10.1016/s0378-1119(00)00210-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Phage display is a widely used method to optimize the binding characteristics of protein-ligand interactions. In addition, it has been used to clone genes from genomic and cDNA libraries based on their ligand-binding characteristics. One difficulty often encountered when expressing heterologous proteins by phage display is the toxicity of the protein on the Escherichia coli host. Previous studies have shown that heterologous protein expression can be tightly controlled using plasmids with the P(BAD) promoter of the arabinose operon of E. coli, and the araC gene, which is both a positive and negative regulator of the promoter. We constructed a set of phage display vectors that utilize the P(BAD) promoter to control the expression of proteins on the surface of the M13 bacteriophage. These vectors exhibit tightly controlled expression of proteins on the surface of the phage. In addition, the amount of protein displayed on the phage is modulated by the amount of arabinose present in the growth medium during phage propagation. This may be useful for altering the stringency of binding enrichment during phage display.
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Affiliation(s)
- W Huang
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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